Dear Yenchun,

According to your case, there are two major points worth considering.
First, you believe that the oxide was completely removed based on the etch
rate, I would suggest you to do HF dipping to make sure that no oxide left
(if you haven't done so). Doing an XPS or AES scan on the surface is
definitely the best way to tell the chemistry. Second, if it is actually a
polymer layer on surface, it may not be a pure CFx or CHx layer. What
is your chamber wall made of? Is your system only used for TEOS etching?
Any other materials or gases had been used for etching previously?
Before proceeding to a special RIE residue solvent, tell me the answers to
the above questions. Perhaps I can recommend you the best way to solve
this problem.

Regards, Isaac

On Mon, 18 Jul 2005, Yenchun Lee wrote:

> Dear Isaac,
>
> I have a very similar problem here. I used RIE to etchback a layer of
> TEOS(@695 degree) oxide with CHF3/CH4/Ar mixture to expose the underlying
> layer of amorphous silicon. Then I found my TMAH can't etch the amorphous
> silicon.  The same amouphous Si without TEOS oxide deposition and RIE
> etchback, can be etched in TMAH perfectly.  From the RIE etch rate, I am
> pretty sure there is no TEOS oxide left on the exposed a-Si.  I am guessing
> there is polymer residue on the amouphous silicon. I've tried O2 ozone PR
> asher following by 10 minutes in Piranha to remove them, but it didn't work.
> Do you have any suggestion to deal with these tough residue? More O2 plasma?